Condensation, damp and mould

No one wants to live in a damp home. Damp can cause mould on walls and furniture and cause wooden window frames to rot. It's also unhealthy.  Some damp is caused by condensation. This can lead to a growth in mould that appears as a cloud of little black dots. For other kinds of damp, see below.

Condensation occurs when moist air comes into contact with a colder surface like a wall, window, mirror etc. The air can’t hold the moisture and tiny drops of water appear. It also occurs in places the air is still, like the corners of rooms, behind furniture or inside wardrobes.

- The main factors that cause condensation in a property are;
- Too much moisture being produced
- Not enough ventilation
- Cold surfaces
- Temperature

You need to look at all of these factors to cure a condensation problem.

First steps against condensation?
Open the curtains and wipe dry your windows and windowsills every morning, as well as surfaces in the kitchen or bathroom that have become wet. Wring out the cloth in a sink rather than drying it on a radiator, or the water vapour is going straight back into the air in the property.

First steps against mould growth? 
First treat any mould in the property, then deal with the basic problem of limiting the amount of condensation you are creating to stop mould reappearing. To kill and remove mould, wipe down or spray walls and window frames with a fungicidal wash or very diluted bleach. Ensure that you follow instructions for its safe use. These fungicidal washes are available at local supermarkets or DIY stores. Wash affected clothes and shampoo carpets.

Produce less moisture;
Hang your washing outside to dry if at all possible, or hang it in the bathroom with the door closed and a window slightly open or extractor fan on. Use a tumble dryer if there is one. If you choose to dry clothes on radiators, the extra cost of heating the resultant damp air in the property will far outweigh the cost of using a tumble dryer to start with.

- Always cook with pan lids on, and turn the heat down once the water has boiled. Only use the minimum amount of water for cooking vegetables.
- When filling a bath, run the cold water first then add the hot - it will reduce the steam by 90% which leads to condensation.
- Never turn bath/shower room extractor fans off by the isolator switch. By turning them off, you are likely to cause damage to the property and incur charges for repairs.

Ventilate your home;
Ventilation dramatically helps to reduce condensation by removing moist air from your home and replacing it with drier air from outside.

- Reduce condensation build up by ’cross-ventilating’ your home - opening to the first notch a small window downstairs and a small one upstairs. They should be on opposite sides of the house. At the same time, open the interior room doors, this will allow drier air to circulate throughout the property. Cross-ventilation should be carried out for about 30 minutes each day.

- Ventilate your kitchen when cooking or washing up. A window slightly open makes a huge difference to condensation. If you have one, use your cooker extractor hood or extractor fan if it is vented outside.
Ventilate your kitchen and bathroom for about 20 minutes after use by opening a small top window. Use an extractor fan if possible - they are cheap to run and very effective.

- Open curtains during the day to allow air to the windows and frames. They will go black with mould if you don’t and will cost a lot to redecorate or reseal.
Ventilate your bedroom by leaving a window slightly open at night, or use trickle ventilators if fitted. (But again, remember your security). Trickle vents are small plastic strips in double glazing frames. Leave these vents open at all times

- Keep kitchen and bathroom doors closed to prevent moisture escaping into the rest of the property.

- To reduce the risk of mildew on clothes and other stored items, do not overfill wardrobes and cupboards, as it restricts air circulation.

- Keep a small gap between large pieces of furniture and the walls.

Heat your home;

Warm air can hold more moisture than cooler air, which is more likely to deposit droplets of condensation round your home. Air is like a sponge; the warmer it is, the more moisture it will hold. Heating one room to a high level and leaving other rooms cold makes condensation worse in the unheated rooms. That means that it is better to have a medium level of heat throughout the house.

- Keeping the heating on at low all day in cold weather will help to control condensation. It will also be more economic than having the heating on full blast for several short periods during the day.

- If you don’t heat every room, keep the doors of unheated rooms open to allow some heat into them and air to circulate.

Condensation is not the only cause of damp

‘Penetrating damp’
 is caused by moisture coming into the house through leaking or cracked pipework, a damaged roof, blocked guttering, gaps around window frames and cracked or defective rendering and brickwork. All these problems can be remedied.

‘Rising damp’ is due to a defective (or non-existent) damp course. This will leave a ‘tide mark’ about a meter above the floor. Fixing rising damp is a job for a qualified builder.

NB: Newly built homes can sometimes feel damp because the water used during its construction is still drying out.

This information is available to download as an easy read leaflet.